My Great Great Grandmother Was the Great Aunt to General George C. Marshall?

My Great great Grandmother was General George C. Marshall's Great Aunt?

One of our family lore's is that Sarah Marshall Jones Dean, my great great grandmother, was the Great Aunt of General George C. Marshall.  I had once done  a little checking to see if I could verify that--and couldn't.  However, following my blog of July 6, 7 and 8, I decided to be a little more thorough in trying to verify the story.  

To be his Aunt, General Marshall would be the son to one of Sarah's sisters.  Thus, one of Sarah's brother-in-laws would be a Marshall.  To be the Great Aunt, the daughter of one of Sarah's nieces or nephews (son or daughter of one of her siblings) would have married a Marshall; and General Marshall would be the son from that marriage.  Obviously, the father had to be a Marshall to provide the Marshall surname.  

Hypothetical Relationship Chart

In the hypothetical chart above, I have depicted the case of Sarah's sister Amanda Wood's daughter Ellen marrying George C. Marshall. Their son's Great Aunt would be Sarah Marshall Jones Dean.  Unfortunately, I can't find any Marshalls in my family tree.  

I went a step further and created a family tree for General George C. Marshall.  Note in the pedigree chart below that George C. Marshall's mother is a Bradford.  I checked my family tree and do not have any Bradford's in the line.  However, Sarah had two sisters, Christiana and Margaret, who I haven't found were married.  If one of them married a Bradford and had a daughter, Laura, she could have married General George C. Marshall's father, also named George C. Marshall.  However, Laura's mother's maiden name was Stuart, as shown below.  So much for that theory.

Marshall Pedigree Chart

It is possible that the relationship of Great Aunt could have been through Sarah's husband, Spear Dean's side of the family; but the stories all say she was the Great Aunt, not that Spear was the Great Uncle.  Additionally, I don't find any of the surnames in the Marshall pedigree going back four generations in my family tree--on the Jones or Dean sides.  

I guess it is possible there were some second marriages that I don't know of or other unusual quirks that could result in Sarah being the Great Aunt; but I haven't found anything yet to confirm it--as much as I would love to!  I am wondering if the story didn't start because she had the middle name Marshall.  However,  since General Marshall was two generations behind her, I am not sure how the Marshall in her name would be related?  It would have come from one of her ancestors--not descendants.

If I have missed something here, I would appreciate your comments